Scanning Thermal Microscope (SThM) is a technique that uses the sample's thermal conductivity as a contrast mechanism in imaging microscopic features. A temperature sensing probe in SThM can be used for semiconductor material and device study such as locating hot spots created by short circuit defects in the sub micron regime.
Commercial SThMs use a miniature thermal resistor positioned at one end of a cantilever. If a small current is passed through the resistor, and the resistance is measured as the probe tip is scanned over a sample surface, a local temperature map of the sample is produced based on the resistance changes. If, on the other hand, a large current is passed and the resistor temperature rises significantly above that of the sample, the probe detects local changes in the local thermal conductivity of the sample. In the latter mode of operation, the thermal conductivity of the sample, as presented at the surface, is an aggregate of any thermal conductivity variations down into the sample. Changes in composition below the sample surface will therefore produce a feature in the thermal map.
One of the limitations to current usage of the above probe is that if one needs to obtain the thermal map of an electrically biased sample, the conductive parts of the sample must be passivated to prevent excessive current leakage between the tip and the conductive sample.
Another limitations to current usage of the above probe is that if one needs to obtain the thermal map of an sample with high spatial resolution, the probe tip must be have a small diameter.
What is needed, therefore, is a probe for a scanning thermal microscope with small tip diameter that can prevent excessive current leakage between the tip and the conductive sample.